1. Field of the Invention
The present invention relates to underwater foils such as foils of a hydrofoil craft, propeller blades of a ship and underwater turbines and blades of a pump moving at high speed under water, and more particularly to low resistance hydrofoils enabling to decrease frictional resistance of the foils by having a lamellar cavitation layer formed on a negative pressure surface of the foils.
2. Description of the Prior Arts
It is known that frictional resistance of a shell plating of a ship against water is decreased by jetting air from an underwater shell plating of the ship and having a lamellar air layer formed on the surface of the underwater shell plating. It has been tried to apply this to a hydrofoil craft.
The hydrofoil craft, however, for which the frictional resistance of foils against water is decreased by jetting air in such a manner as mentioned above, is not put to practical use. The reason for this is that there are great difficulties in setting up an air compressor for jetting air in hydrofoil craft body, necessitating a power for the air compressor and, moreover, mounting a piping and air-blowoff holes in the foils themselves.